in an imperceptible manner or to an imperceptible degree; the power of the Secretary of State in London increased gradually but imperceptibly
[ Syn: unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably , unnoticeably ]